The results of this survey indicate a high prevalence of obesity and a low prevalence of physical activity among endometrial cancer survivors. In our sample, 16% of the respondents were overweight (BMI between 25 and 30), and 50% were obese (BMI ≥30). Comparing this the National Health and Nutrition Examination Survey (NHANES),20
this sample of survivors has a higher prevalence of obesity than women in the general U.S. population. Given the age distribution in our sample, we would expect that approximately 32% of the women would be overweight and 35% would be obese. Given the importance of obesity as a risk factor for endometrial cancer, this is not surprising, but it does indicate a need for interventions to manage weight and related co-morbidities in this population.
Only 22% of the sample was physically active at the level of current public health recommendations, compared to 46% in the general U.S. population.21
This difference might be partly explained by the older age of our sample. National data show that older adults have lower rates of physical activity (41% for women age 65–74 and 33% for women 75 and older22
). Other surveys of cancer survivors have also found a higher prevalence of physical activity.7, 23
Lower physical activity in our sample also might be explained by the high prevalence of co-morbid conditions, particularly musculoskeletal complaints.22
Physical activity was associated with physical functioning, fatigue, and pain, although the relationship with pain was attenuated after adjusting for musculoskeletal conditions. This mirrors the findings by Courneya et al.,7
who found that endometrial cancer survivors who exercised at recommended levels had better overall quality of life, physical well-being, functional well-being, and social well-being and less fatigue. However, that study did not separate individuals who exercised at levels below public health recommendations from those who did not exercise at all. In examining this group separately, we found no significant differences in physical functioning and pain between the somewhat active group and participants whose physical activity met public health guidelines. This result is similar to findings from the BRFSS, which showed that any activity at all is associated with better physical and mental health.24
For fatigue our results indicate that the somewhat active group had higher fatigue than the active group. Furthermore, there was a significant BMI × physical activity interaction, showing that the expected positive relationship between physical activity and fatigue occurred primarily among participants with a normal BMI. This suggests that although even modest increases in activity could have a positive effect on functioning and pain, activity sufficient to produce fitness improvements and/or weight loss may be needed to decrease fatigue.
BMI and physical functioning were related, as hypothesized, but the associations between BMI and pain and fatigue were not significant when physical activity was included in the model. This is at odds with the study by Courneya et al,7
which found a strong relationship between fatigue and BMI, but no relationship between BMI and overall quality of life, physical well-being, functional well-being, emotional well-being, or social well-being. Such differences could be due to differences in the measures used.
Several observational studies have shown associations between physical activity and colon and breast cancer recurrence.25–27
A relationship with endometrial cancer recurrence has not been studied, although such a link is biologically plausible. The insulin pathway is one possible mechanism. High levels of insulin can stimulate tumor development in the endometrial tissues by reducing levels of insulin growth factor binding protein-1. This increases levels of insulin growth factor-I (IGF-I) activity, which has been linked to proliferative activity in the endometrial tissue.5
Physical activity could assist endometrial cancer survivors with insulin regulation. A study of the effects of exercise training on insulin, insulin resistance, insulin-like growth factors, and insulin-like growth factor binding proteins in breast cancer survivors found that exercise decreased IGF-I,28
Efforts to increase physical activity and address obesity face a number of challenges, several of which are highlighted in this study. Endometrial cancer survivors’ co-morbid health problems complicate the adoption of physical activity and require tailored intervention approaches, including adaptation of activities to accommodate comorbid health problems such as musculoskeletal conditions. The cancer diagnosis has been identified as a ‘teachable moment” by other research.23, 29
Indeed, in our study survivors further from diagnosis appear to be slightly less likely to be sedentary and obese, indicating that they may change their behavior in response to cancer diagnosis and treatment and may be receptive to programs to help them change health behavior and manage weight if warranted.
This study has potential limitations that should be noted. One is that our response rate was only 61%. This compares favorably, however, with other cancer survivor surveys reported in the literature,7, 23
and our analysis of differences between respondents and non-respondents did not reveal any serious selection biases. A second limitation is that our question about comorbid health problems was open ended and relied on respondent recall. A structured questionnaire to query respondents about health problems may have been more accurate and provided additional information, such as the severity of the health problem. However, we recognized that survivors would be less likely to respond to a lengthy survey, and because our intent was to obtain only a brief description of the comorbid health problems rather than a detailed inventory, we sacrificed some precision in the reporting of health problems for a higher response rate. Future studies could be done to more clearly delineate the relationship between the comorbid health problems and physical activity in this population. Third, we relied on self-reported weight and height to calculate BMI. Self-report data often underestimates BMI, especially among older and more overweight individuals.30, 31
If some respondents who are actually obese were misclassified as normal weight or overweight, this likely would have reduced the size of the relationship between BMI and outcomes. Finally, this is a cross-sectional study, and although the relationships we have found indicate associations, causality cannot be demonstrated. We found relationships between physical activity and functional outcomes, but one could speculate that either physical activity improves physical functioning, fatigue, and pain or poor physical functioning, fatigue, and pain causes cancer survivors to be less active. Indeed, both are probably true to some extent. However, exercise has been used successfully as an intervention for survivors of other types of cancer and has been shown in randomized studies to improve these outcomes.32–37
Such findings, along with the relationships uncovered in this survey of endometrial cancer survivors, indicate that exercise may be a helpful component of quality of life and disease prevention interventions for this population.